Call it a ‘gut print’. The collective DNA of the microbes that colonize a human body can uniquely identify someone, researchers have found, raising privacy issues.

The finding1, published in Proceedings of the National Academy of Sciences on 11 May, suggests that it might be possible to identify a participant in an anonymous study of the body’s microbial denizens — its microbiome — and to reveal details about that person’s health, diet or ethnicity. A publicly available trove of microbiome DNA maintained by the US National Institutes of Health (NIH), meanwhile, already contains potentially identifiable human DNA, according to a study2 published in Genome Research on 29 April.